Tropical Rainforests
•Climate
•Distribution of Rainforest
•Structure of the Forest
•Plant adaptations
•Threats to the forest
•Useful products
Distribution of Rainforests
Climate
The temperature averages 2830°C all year but gets warmer in
March and September when the
sun is not directly overhead and
there is less cloud.
There is a convectional storm
almost every afternoon except in
March and September when,
because there is less sunshine,
there is less evaporation so the
atmosphere is not so full of
moisture and there are fewer
clouds.
The climate is described as humid
Climogram for Manaus,Brazil
250
30.5
30
29.5
150
29
28.5
100
28
50
27.5
0
27
jan
feb
mar
apr
may
jun
jul
aug
Months
Rainfall
Temperature
sep
oct
nov
dec
Temperature (C)
Precipitation (mm)
200
Structure of the Forest
There are 5 layers in the forest
Emergents
Canopy
Under canopy
Shrub layer
Groundlayer
Structure of the Rainforest
EMERGENT TREE
CANOPY
UNDER CANOPY
SHRUB LAYER
GROUND LAYER
Plant adaptations
1. Emergents and 2. the Canopy
Many plants have waxy leaves and ‘drip tips’ to
allow heavy rainfall to run off.
The canopy and the emergents have buttress
roots, to anchor the tree.
Large leaves and dark green foliage to maximise
photosynthesis.
These emergent trees grow to over 40m as they try
to gather the maximum amount of sunlight.
The canopy forms a closed layer which allows little
light through.
There is a huge amount of growth in all layers every
year.
The increase in the Biomass is balanced by the
amount of decay. This is Nutrient cycling. This can
be shown in a Gersmehl Diagram. (see slide 15)
3. The under canopy
In this layer plants have to be
shade tolerant; they have very big
and very dark green leaves.
There are often few branches on
the tall, straight trunks.
Flowers are very bright to attract
insects; the air is too still for wind
pollination.
There are sometimes parasitic
plants living on the trunks of trees:
they get their food from the host
tree.
Many of the plants have valuable
fruits such as Brazil nuts,
bananas, mangoes, rubber
4. The shrub Layer
In this layer the shrubs are bushy
and have many stems
Shrubs have dark green leaves at
the top of the plant
The plants are shade tolerant
They often have bright flowers
which are strongly scented
Tea, coffee and cocoa are crops
that grow naturally in this layer
5. Ground Layer
It is very dark on the forest floor
Ferns and orchids are common plants at this level. Some
of the plants are parasitic.
There are many gaps between plants but it is very
difficult to get around due to the tangle of vines and
dead, fallen branches. The Litter layer is quite thick but
Plant and animal material decays quickly in the hot,
humid conditions. This is the Litter layer.
Threats to the Forest
An area of forest the size
of Belgium is clear felled
for timber every year
Local people have growing
populations and need
farmland
Timber from the tall,
straight trees is much
sought after for building
and for furniture
Big business wants to
extract resources from
under the forest
Hydro-electric schemes
flood the forest
Accidental fires burn out of
control
Satellite image of deforestation in the Amazon region, taken
from the Brazilian state of Para on July 15, 1986. The dark
areas are forest, the white is deforested areas, and the gray
is regrowth. The pattern of deforestation spreading along
roads is obvious in the lower half of the image. Scattered
larger clearings can be seen near the center of the image.
Glossary
Biomass: Living and dead matter produced, including plants and animals. (Kg/m2/annum)
Canopy: The highest layer of the rainforest, made up of the tops of trees. Animals such as
howler monkeys, red-eyed tree frogs, sloths and parrots live here.
Equator: An imaginary circle around the earth, equally distant at all points from the North and
South poles. It divides the earth into two halves - the Northern and Southern Hemispheres.
Emergent: The tops of the tallest trees in a rainforest.
Evaporate: When moisture changes from liquid to gas in the air.
Extraction: To remove something (for example, to take out Brazil nuts from the Amazon
rainforest).
Forest Floor: The ground layer, made up of tree roots, soil and decaying matter. Mushrooms,
earthworms, and elephants all make their homes here.
Greenhouse Effect: The warming of the planet caused by chemicals which trap heat in the
air. This process is being sped up by humans who put too many heat-trapping chemicals into the
air. Some causes include car exhaust, factory smoke, and burning rainforests.
Interdependence: The concept that everything in nature is connected to each other, and
cannot survive without the help of other plants, animals and abiotic factors (such as sun, soil,
water and air) around it.
Nutrients: Food needed for growth by living things.
Species: A distinct kind of plant or animal that has many common characteristics or qualities.
Sustainable: Using products of the forest in a way that does not permanently destroy them,
so that people in the future can also use them.
Tropic of Cancer: A circle around the earth, parallel and to the north of the equator.
Tropic of Capricorn: Similar to the Tropic of Cancer, but to the south of the equator.
Understorey: The second layer of rainforests, made up mostly of young trees and shrubs.
Animals that live here include jaguars, tapirs, snakes, and woodpeckers.
Additional Glossary
Buttress roots – wide spreading roots like scaffolding that support the very tall emergent and
canopy trees.
Climogram- a graph that shows temperature and rainfall on double axes. This is useful for
describing climate and comparing the climate of two or more places.
Convectional storm - rain that is the result of early evening cooling of moist air so that the
vapour condenses and a short heavy storm happens
Humid- the air is almost saturated with moisture and cooling a small amount will result in rainfall
Nutrient Cycling – the process of material dropping to the forest floor, decaying and the
nutrients being added to the soil then being taken up by plants to make new growth.
Parasitic- a plant or animal that lives on and gets its food from another species
Photosynthesis- the biological process that uses sunlight, water and carbon dioxide to
produce food for the plant and oxygen. The plants need to have Chlorophyll in their leaves for this
to happen
Useful Products
It is difficult to know how many useful products come from the rainforest;
many species of plant and animal have yet to be studied.
However we do know of many food crops such as coffee, cocoa, tea,
Brazil nuts, Oil palms, coconuts etc. that are found in tropical forests and
can be farmed and harvested.
Raw materials such as Copra, Sisal, Hemp, Mahogony, Teak, Rubber are
all rainforest crops
There are huge deposits of useful minerals under the forest e.g. Iron ore,
Bauxite, Gold, Silver, Tin and Diamonds
The high rainfall and fast flowing rivers make Hydro Electricity cheap once
the dams and generators have been installed.
Many medicines such as quinine for Malaria, Aspirin and several anticancer drugs have been extracted from Rainforest plants.
Gersmehl Diagram for the
Rainforest
Sunlight
Animal waste + Decay
Biomass
Harvest
Leaf fall
Back to Emergents slide
Each circle represents a
store of nutrients.
Each arrow represents a
flow of nutrients.
The size of the circle is
proportional to the volume
of nutrients stored.
Litter
Nutrient Take up
Water
Decay
The width of the arrow is
proportional to the volume
of nutrients flowing along
that route.
Soil
Erosion
Weathered
Rock